Over at Slate, William Saletan has finished a wonderful series on the distortions and dishonesties of memory. Although our memories always feel true, they’re extremely vulnerable to errant suggestions, clever manipulations and the old fashioned needs of storytelling. (The mind, it turns out, cares more about crafting a good narrative than staying close to the truth.) Needless to say, this research has profound implications for everything from eyewitness testimony to talk therapy.

After opening with a clever mass experiment – Slate doctored a few political photos, and then demonstrated that a significant percentage of respondents “remembered” the fictional events – Saletan went on to describe the science behind this sentimental delusions. He focused in large part on the important and influential work of Elizabeth Loftus:

The researchers showed these ads to a group of college students, while other students saw a non-Disney ad instead. To ensure that the Disney ads wouldn’t trigger true memories of shaking Mickey’s hand, the researchers screened out students who reported up front that they had met a TV character at a theme park.

Of the students who were shown an ad featuring happy memories of meeting Mickey, 90 percent later reported increased confidence that this event had happened or might have happened to them. That was twice the percentage who reported such an increase in the control group. And compared with the control group, those who saw the Disney ad were significantly more likely to say that they fondly remembered visiting the park and that such visits had been central to their childhoods. Many who saw a different version featuring Bugs Bunny were convinced that they had met him at Disneyland, even though this was impossible, since he was a Warner Bros. character.

One of the things that makes this research on the fallibility of memory so interesting is that we can now begin to explain the cognitive flaw at a cellular level. In recent years, there’s been a lot of research in the reconsolidation of memory, or how our the neural representation of our memories is constantly being altered. (Freud called this process Nachtraglichkeit, or “retroactivity”. I write at length about it in the Proust chapter of Proust Was A Neuroscientist.)

It all began with a set of extraordinary experiments done in 2000 by Karim Nader, Glenn Shafe and Joseph LeDoux at NYU. To make a long story short, the scientists demonstrated that the act of remembering changes our memories. Nader, et.al. proved this by conditioning rats to associate a loud noise with a mild, electrical shock. (When it comes to pain, the mind is a quick learner.) As predicted, injecting a chemical that stops new proteins from being created also prevented the rats from creating a fearful memory. Since their brains were unable to connect their context to the electrical shock, the shock was always shocking.

But Nader, Ledoux and Shafe took this simple experiment one step further. First, they made sure that the rats had a strong memory associating the shock with the noise. After letting this memory solidify for up to 45 days, they re-exposed the rats to the scary noise and injected a protein inhibitor into their brain. But what made their experiment different was its timing. Instead of interrupting the process of making a memory, they interrupted the process of remembering a memory, injecting the noxious chemical at the exact moment the rats were recalling what the noise meant. According to the dogma of remembrance, nothing much should have happened. The long-term memory should exist independently of its recall, filed away in one of the brain’s protected file-cabinets. After the poison is flushed out of their cells, the rats should remember their fear. The noise should still remind them of the shock.

But this isn’t what happened. When Nader, et.al. blocked the rats from remembering their fearful memory, the original memory trace also disappeared. After only a single interruption of the recollection process, their fear was erased. The rats became amnesiacs.

At first glance, this experimental observation seems incongruous. After all, we like to think of our memories as being immutable impressions, somehow separate from the act of remembering them. But they aren’t. A memory is only as real as the last time you remembered it. The more you remember something, the less accurate the memory becomes. The larger moral of the experiment is that memory is a ceaseless process, not a repository of inert information. It shows us that every time we remember anything, the neuronal structure of the memory is delicately transformed, or reconsolidated. And that is why it’s so easy to convince naive subjects that they met Bugs Bunny at Disneyland.

Comments

I’ve been listening to an Intro to Psychology class by Paul Bloom (http://academicearth.org/lectures/bloom-intro-to-psychology) and he cites research that was done that shows that alot of people have a false memory of where they were when the World Trade Center was hit. Even a memory like that can be falsified!

He cites some psychologists (can’t remember who) that had a clever idea days after the WTC was hit to go out and ask hundreds of people where they were the other day when the WTC was hit. They then tracked these people down a few years later and asked them the same question again, and many of them gave different answers!

If we can’t trust a memory as seemingly strong as this, what can we trust? Scary.

William James, as quoted in “Memory”, by Squire and Kandel, made a distinction between short-term memory and long-term memory by observing that long-term memory can last a lifetime. Looking at long-term memory from my present age,(62), I correctly recall performance limits, (numbers), of aircraft I flew in the 1960’s. Attempting to visualize an individual flight from a logbook date has faded to being able to remember the point of departure, the destination and scant specific detail, of the weather along the the flight. Navigational details, again mostly numerical in nature, is also recallable.

PW, I’m familiar with the study that you mentioned and it surprised me too. I would think that intense experiences would be more likely to be remembered accurately (wouldn’t this have an evolutionary advantage?), but the flashbulb memory research that I have read shows that it is just as prone to error as incidental memory. I think that it is important to mention that in addition to being an influential researcher, Elizabeth Loftus is a law professor at UC Irvine. Separating truth from false memories (especially after botched psychotherapy, where the moment of insight may produce the false memory) seems like a task as daunting as it is important in separating the innocent from the guilty. I am an undergraduate at Northwestern currently studying with Peter Rosenfeld, who uses ERPs (P300) to detect deception and malingering. Although the paradigm works best for people feigning brain injury, it would be interesting to see if it can detect false memories. It would also be interesting, however, to find that the subjective truth-value of the memory is the more important factor and can beat the detector (this has been shown in word recall studies with words that were not learned, but were related to learned words vs. unlearned non-related words).

Is it possible that the mutability of memories could result in more accurate memories under certain conditions? It’s commonly noted that repeated experience in specific tasks or situations leads to finer and more accurate observation within those tasks/situations, and insight into/about an earlier experience could be due to a more detailed reconstruction made possible by information collected and retained from intervening experiences.

Fascinating stuff. I had a global brain injury 3 years ago from which I have remarkably recovered beyond what any of the medical community predicted thanks to nueroplasticity, own efforts, and alternative therapies.

At first, I did not have much long term memory at all. It came back in bits and pieces and is very random. For instance, I can remember every word to some annoying song, but cannot remember in detail the births of my children. The pictures of such events become my memories.

So, I am wondering now if it is the actual memories that are just gone or is it the process of remembering that is being interrupted? In any case, sounds like I do what is most common…I embellish.

Chogyam Trungpa Rinpoche, Tibetan meditation master, opens his liturgy for beings trapped in the Dark Age with the following lines:

“..In the spontaneous wisdom of the trikaya (body, speech, and mind of the Buddha), I take refuge in order to free those who suffer at the hands of the three lords of materialism (seeing the world in terms of what’s in it for ‘me’), and are afraid of external phenomena which are their own projections.” …Sadhana of Mahamudra, CTR

So, it’s not only memories but ideas that we also project as overlays on top of sense perceptions in the moment or ideas we have about the future.

George W. Bush also has shown problems with correctly recalling what he was doing on 9/11, what he saw and who told him about the attacks. There was a great piece in Applied Cognitive Psychology about this in 2004 by Daniel L. Greenberg. A PDF of this can be found at http://www.planet1337.com/stuff/flashbulb.pdf.

I think the phrasing- ‘interrupted the process of remembering’ is a bit confusing. I took it to mean that the researchers prevented retrieval, when I think you mean just that they interfered with the reconsolidation. I checked the paper to be sure and the rats were played the CS and then immediately given the protein synthesis inhibitor. All the rats froze (i.e. remembered). It was only on subsequent retest that the memory was gone.

Fascinating. This is what the Eastern scriptures and sages have been claiming for thousands of years! Finally, science has found a way to prove it. Great to see the east and west approach increasingly prove each other. For some reason the modern approach berates anything we can directly observe ourselves, unless it is proven in a lab. Of course not all direct observations are reliable – but the observation that they are not reliable is clearly valid! Thats is a basic assumption in science and resonates with the principle of Maya (illusion) that the Hindus refer to in describing the world as an appearance and our essence as consciousness/awareness.

This feels like it’s on the right track. I’m like Scott Yates – I kind of assumed I couldn’t remember much about my childhood, but when my daughter was born and I started having more reasons to think and talk about it again, suddenly I could “remember” more childhood events. It turns out I was a secret agent working for the Mossad.

Given that nervous systems are literally bundles of looped circuits round which electrochemical pulses flow, I find it very comforting that researchers are coming round to the view that memory is about repeated, fluid activity rather than static records imprinted on dormant assemblies of neurons. Thanks for the post!

Re #12: 45 days is surely long enough for the memory to be consolidated.

These manipulations during reconsolidation are based on earlier research during consolidation, where for only a critical period (< 8 hours i believe) the initial memory can be wiped out through manipulations of the hippocampus with drugs or shock treatments.
The interesting thing about these recent studies is that the drug treatments work again only if the memory is retrieved first.

I am a psychiatrist who does a lot of psychotherapy. In therapy, this is a common phenomenon. People recall different versions of events from the past, all of them meaningful in different ways. Sometimes I equate the process of therapy with peeling the layers of an onion. The goal is not to reach some ‘core of truth’, but rather to understand the layers of meaning.
Donald Spence writes about narrative truth in his book, and shows how it is often not the historical truth of say a traumatic event that matters, as much as the story one weaves to explain it. Our mind needs to make sense of events through coherent narratives, essentially storymaking.

Could it be that the “poison” simply destroyed the “links” to the memories and not the memories themselves? From this article, I can’t see any reason to say definitively that recalling the memory destroyed the memory. What am I missing?